As work progresses on building a smarter grid, we’ll need to take a fresh look at existing technologies, even as we invent new ones, writes Jean Philippe Faure, chair of the IEEE 1901 broadband over power line committee, and Jim LeClare, chair of the IEEE 1901.2 Low-Frequency narrowband power line communications working group.
Many existing technologies, once thought to have limited applications and an uncertain future – even serious drawbacks – can be tweaked to provide viable and valuable technical options in a smart grid that demands flexibility.
A case in point is Power Line Communication or PLC, a blanket term that covers several technical approaches to sending a modulated signal over transmission, distribution and/or premise wiring for a variety of communication purposes for monitoring and control, including smart metering and myriad smart grid applications.
PLC’s properties found initial success in specific circumstances where legacy equipment meshed with its strengths. Objections to its wider use have largely been based on two main, intrinsic hurdles.
Transmission, distribution and premise wiring generally is designed for transmitting AC power in 50 hertz (Hz) and 60 Hz cycles, with limited ability to carry signals in higher frequencies, such as PLC’s traditional signal in the 1.6 MHz to 30 MHz range.
This property could limit signal propagation from one point to another. The other main objection to PLC has been that, in many cases, it runs on unshielded wires that have the potential to emit radio signals and many if not most countries have laws that forbid such interference with other uses of those frequencies.
The “good news,” if you will, is that years ago the IEEE Standards Association (IEEESA) set out to improve PLC and harmonize its proprietary flavors. To do so, the IEEE P1901.2™ Working Group examined PLC’s strengths and optimized them for smart grid applications, and addressed PLC’s real and perceived shortcomings to make it a suitable medium for smart grid. The intended outcome of this standards-based work also provides the flexibility and scalability needed to serve applications needed for smart cities and the Internet of Things.
That’s quite a leap for a communication medium that many had considered passé or possessing a geographically limited future.
History meets new challenges
PLC for voice telephony began in the early 20th century and became widespread in Europe and the United States by the end of the 1920s.
In the smart grid era, which required first one-way, then two-way data transmission over power lines, Echelon (which has since focused on industrial IoT technology) used PLC for low-frequency, low data rate (sub 1Kbps) smart metering projects in Italy, starting around 2000, and more recently a higher data rate (sub 50Kbps Cenelec data rates) PRIME OFDM PLC technology for Spain, along with G3-PLC OFDM PLC installations in France and Japan (also with sub 50Kbps Cenelec data rates).
Echelon performed similar installations in Scandinavia and Eastern Europe. Reliability…